I just picked up on this thread.....yes, ghost shrimp CAN eat your fry. I had several beautiful red wag platy fry in my large tank, and I came home from school one day to find a ghost shrimp sitting on top of one of my plants eating one of the fry. i quickly moved all the fry into my smaller tank. Ghost shrimp will get more aggresive as the water temperature rises; at 70F, they are much more lethargic and laid back than they are at 80F. I keep my tanks around 78F, but I've never had a problem with my shrimp attacking anything else. To keep your tank clean, you might want to pick up an algae eater or two; I have 4 in my 20, and they have finished cleaning the algae of the sides of the tank, so they swim around and clean individual pieces of gravel now as well. I've also noticed my clown loaches cleaning gravel too.
Oh yes, and ghost shrimp are freshwater shrimp, also known as glass shrimp. They're larger than brine shrimp, which ARE saltwater shrimp. Brine shrimp are very closely related to SeaMonkeys.